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Appl Environ Microbiol. 1974 November; 28(5): 785-792
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Effects of Seawater Cations and Temperature on Manganese Dioxide-Reductase Activity in a Marine Bacillus

Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12181

ABSTRACT

The seawater cations, Na⁺, K⁺, Mg²⁺, and Ca²⁺, each stimulated MnO₂-reductase activity of whole cells and cell extracts of Bacillus 29. Concentrations of Na⁺ and K⁺ which stimulated whole cells and cell extracts maximally were equivalent to those in two- to fivefold diluted seawater. Cell-extract activity was strongly stimulated by Ca²⁺ and Mg²⁺ up to a concentration of 0.01 M Mg²⁺ and 0.002 M Ca²⁺, with little additional stimulation above these concentrations. Whole-cell activity was stimulated biphasically with increasing concentrations of Ca²⁺ and Mg²⁺. Comparison of the effects of individual cations or mixtures of them at concentrations equivalent to their concentration in fivefold diluted seawater showed that more activity was obtained with 0.01 M Mg²⁺ or 0.002 M Ca²⁺ than with 0.1 M Na⁺, and more with 0.1 M Na⁺ than with 0.0022 M K⁺. Fivefold diluted seawater permitted as much or more activity as solutions of individual or synthetic mixtures of the cations. Pre-exposure experiments showed that the ionic history of whole cells was important to their ultimate activity. The MnO₂-reductase activity of induced whole cells exhibited a temperature optimum near 40 C. Cell extracts had different temperature optima (T_opt), depending on whether induced glucose-linked activity (T_opt = 25 C), uninduced glucose-linked, ferricyanide-dependent activity (T_opt = 30 C), or uninduced ferrocyanide-linked activity (T_opt = 40 C) were being measured. Some of these optima are higher than previously reported.

¹ Present address: Department of Agronomy, Cornell University, Ithaca, N. Y. 14850.